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Physical Matching of Metals: Grain Orientation Association at Fracture Edge |
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| Authors: | Barbara K. Lograsso Ph.D. |
| Affiliation: | Midwest Forensics Resource Center, Ames Laboratory, 127 Spedding Hall, Ames, IA, 50011 Additional information and reprint requests: Barbara K. Lograsso, Ph.D. Midwest Forensics Resource Center Ames Laboratory 127 Spedding Hall Ames, IA 50011 E-mail: bkl@ameslab.gov |
| Abstract: | The objective of this study was to examine whether surface crystal orientation can be used to associate or differentiate metal fracture fragments. The orientations of individual crystals and crystals across the fracture plane were measured on polished steel and iron alloy surfaces using Electron Backscattered Diffraction/ Orientation Imaging Microscopy (EBSD/OIM). This investigation examined crystallographic characteristics within a metal. This study showed that for transgranular fracture, it is feasible that pieces of grains could be associated across the fracture surface with the difference in orientation between grains (misorientation) along a length sequence of grain orientations on one side of the fracture surface to associate the other side of a fracture surface. Regarding pair comparisons of crystals on fracture surfaces, it was estimated that the probability for an ordered sequence of six distinct oriented grains along a fracture surface to occur again is about 1 in 4.82 (10)30 or 2.07 (10)−31. |
| Keywords: | forensic science physical match metal fracture metallurgy materials |